<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>下拉菜单</title>
</head>
<body>
  <!-- selected嵌套option, select是下拉菜单整体, option是下拉菜单的每一项 -->
  城市:
  <select>
    <option>北京</option>
    <option selected>上海</option>
    <option>广州</option>
    <option>深圳</option>
  </select>
</body>
</html>